Advanced Question Reentry Anticipation

[Nemoricus]

I'm planning on running a series of tests with a number of different spacecraft, mostly capsules, to see how they behave with different reentry conditions.

While I can directly figure out most things like the reentry angle and speed at entry interface, I'm not sure how to determine the reentry anticipation from the spacecraft's position at entry interface and ultimate landing site.

Any thoughts on this matter?

 

[Urwumpe]

It is just the angular distance around the great circle of over entry interface and landing site. Anticipation = 360° would be once around Earth.

 

[Nemoricus]

Hmm....right, but how does one go from coordinates on the sphere to the angle of the arc of that great circle? I hope that I'm not just missing something really obvious here.

 

[Urwumpe]

Hmm....right, but how does one go from coordinates on the sphere to the angle of the arc of that great circle? I hope that I'm not just missing something really obvious here.

Look at a clock. You have two arrows there...what is the angle between the two arrows? The great circle is a 2D object, like all circles. A cut through the sphere, that passes through the center of the sphere and two points.

 

[Nemoricus]

http://en.wikipedia.org/wiki/Great-circle_distance

I've found what I was looking for. It's about what I expected, too. Non-Euclidean geometries are interesting.